This invention relates to a contact medium which is disposed at the leading end of a probe of an ultrasonic flaw detector and interposed as an ultrasonic propagation medium between the probe and an object under test.
In the conventional ultrasonic flaw detector, such wet contact medium as water, oil, or glycerin has been adopted as an ultrasonic propagation medium between the probe and an object under test.
When water is used as the contact medium, the so-called water-immersion testing method is adopted which requires the sensor part of the ultrasonic flaw detector and the object under test to be kept under water or, as disclosed in Japanese Patent Application Laid-open SHO 55(1980)-55,248, the device is utilized which requires a bag of such ultrasonic-pervious film as PVC sheet to be attached to the leading end of the probe and this bag to be filled with water.
When oil or glycerin is used as the contact medium, this contact medium is directly applied on the surface of an object under test.
In any of the cases mentioned above, therefore, there is a possibility that the object under test will be smeared with the wet contact medium or caused to gather rust or yield to corrosion and, at the same time, part of the ultrasonic flaw detector will be deteriorated or damaged by the wet contact medium.
Further, when the object under test happens to possess surface irregularities or sharp corners, there is a possibility that the ultrasonic-pervious film will sustain a rupture and consequently entail leakage of a wet contact medium and, as the result, the operation of the ultrasonic flaw detector will no longer be effectively continued. In the case of such a material as Teflon (tetrafluoroethylene) which is applied on a given surface only with difficulty, there is a disadvantage that the wet contact medium cannot be conveniently interposed between the probe and the object under test.